This invention relates to antigens having immunogenic determinants of Group B Streptococcus bacteria, to vaccines protecting against those bacteria, to methods of making such vaccines, and to methods of preparing oligosaccharides from bacterial polysaccharides. As used in this application, the term Group B Streptococcus (or GBS) bacteria is used as understood by those in the field, particularly with reference to Lancefield, J. Exp. Med. 108:329-341 (1938) and subsequent work further characterizing Group B serotypes, e.g. Russell-Jones, J. Exper. Med. 160:1476 (1984). The term specifically includes bacteria taxonomically designated Streptococcus agalactiae.
GBS are a recognized etiological agent for bacteremia and/or meningitis in infants, and for infections in adults. Baker, "Group B Streptococcal Infections" in Advances in Internal Medicine, 25:475-500 (1980). Accordingly, it is important to develop rapid and definitive assays for diagnosis of GBS infection, and methods of generating protection against GBS, particularly in infants and compromised individuals.
The GBS capsular polysaccharides are known to be important to GBS virulence and immunity. Baker, cited above. Moreover, the recognized GBS types and subtypes have chemically related but antigenically distinct capsular polysaccharides having a repeating structure composed of galactose, glucose, N-acetyl glucosamine, and N-acetyl-neuraminic (sialic) acid. Baker, cited above. Type III GBS capsular polysaccharide is composed of a backbone made up of repeating branched pentasaccharide units. Jennings et al., Canadian J. Biochem. 58:112-120 (1980).
One study of type III GBS polysaccharides suggests that the natural immunodeterminant site is located at the side chain-backbone junction. Jennings et al., Biochemistry 20:4511-4518 (1980). The presence of the side chain terminal N-acetyl-neuraminic acid residues reportedly was critical for immunodeterminant expression.
Studies of GBS protein immunogenicity are also reported. Lancefield et al., J. Exp. Med. 142:165-179 (1975) report that the so-called C proteins of GBS are capable of inducing protective antibodies when present as an immunogen on a whole organism. The nomenclature "C proteins" is used as defined by Henrickson et al., J. System Bacteriol. 34:500 (1984), and the term includes proteins formerly designated Ibc proteins.
Molecular studies of C proteins have shown that these substances constitute a complex group of proteins of variable molecular weight. Wilkinson et al., Infect. Immunol. 4:596-604 (1971); Bevanger et al., Acta Path. Microbiol. Scand. Sect. B, 87:51-54 (1971); Russell-Jones et al., J. Exp. Med. 160:1476-1484 (1984). Bevanger et al., Acta Path. Microbiol. Scand. Sect. B, 89:205-209 (1981).
Wilkinson et al. disclose that hot acid extracts of whole type Ic GBS yields 13 proteins of varying molecular size (determined by polyacrylamide gel electrophoresis) having serological reactivity in agar gel against type Ic antisera. Bevanger et al. (1979) disclose GBS acid extract containing nine trypsin sensitive proteins and five trypsin resistant but pepsin sensitive proteins. Bevanger et al. (1981) disclose immunogenicity of partially purified acid extracted proteins. Russell-Jones et al. disclose extracts containing up to 30 proteins varying in molecular weight from 20,000 to 130,000, the 130 kd protein being predominant. Russell-Jones et al. also report that multiple proteins reacted by immuno (Western) blot to a single monoclonal antibody, suggesting that some proteins were breakdown products of others. Using another monoclonal antibody, the 130,000 MW proteins and 12 other proteins spaced between 10,000 and 120,000 MW appeared to share a common epitope.
Insel and Andersen, J. Exp. Med. 163:262 (1986) disclose conjugating Haemoplilus influenzae capsular polysaccharide to a protein carrier in an effort to convert the capsule to a more thymus-dependent immunogen.